1. Field of the Invention
The present invention relates generally to a catalyst and more particularly, to a specific component of a catalyst used for polymerization of .alpha.-olefins in high yield and a process for the preparation thereof.
2. Description of the Prior Art
It is known in the art that catalytic components formed by pulverising pure titanium trichloride can be used for polymerization of .alpha.-olefin having at least 3 carbon atoms, as for example, propylene. These components can be obtained by reducing titanium tetrachloride with hydrogen or metallic titanium; by pulverising a solid chloride having a composition corresponding substantially equal to Ti.sub.3 Al Cl.sub.12, which is obtained by reducing titanium tetrachloride with metallic aluminum; or by pulverising a mixture of pure titanium trichloride or the solid chloride having the composition corresponding substantially equal to Ti.sub.3 Al Cl.sub.12 with an organic ether and/or other known components such as an electron-donative compound.
In the preparation of a polymer of .alpha.-olefin, e.g., polypropylene, when the yield of the crystalline form of the high-polymer is improved, there is also a concomitant improvement in the yield of the overall final product and in the quality of the final product. Conventionally, in polymerization of .alpha.-olefins, the yield of the crystalline polymer is more greatly influenced by changes in the properties of the catalytic component than it is by correspondingly significant changes in either the polymerization conditions or the polymerization method. However, the yield is influenced to some extent by the choice of polymerization method or polymerization conditions. Therefore, the improvement of the properties of the catalytic component is a significant problem not only to manufacturers of catalysts, but also to manufacturers of polypropylene.
The present inventor proposed a process for the preparation of a catalytic component for polymerization of .alpha.-olefins which included the steps of forming the reaction product of titanium tetrachloride and an organic ether, adding it to titanium trichloride or a composition comprising titanium trichloride and a metal halide, and then conducting a pulverising treatment. While this technique did improve the properties of the final product of the reaction, it still was not totally satisfactory. Consequently, it would be most desirable to have a new catalyst which further improves the product quality.